This invention relates to a screening apparatus and method of the type that may, for example, be used to screen aircraft-hold luggage for concealed weapons or explosive devices.
It is known from International Published Patent Application WO-A-9309512 to provide an object-based 3D X-ray imaging technique that based upon the principal of imaging objects/regions within an item by detecting discontinuities in the opacity to the transmission of X-rays from different directions surrounding the item. This technique is based upon taking approximately ten views through the item with those views being uniformly distributed in solid angle.
Whilst the above mentioned imaging technique is capable of imaging weapons within aircraft-hold luggage, it suffers from the disadvantage that the uniform distribution in solid angle of the views requires an extremely bulky device to operate upon luggage sized items and would be ill-suited to anything other than piecewise operation.
European Published Patent Application EP-A-0,485,872 discloses a baggage security screening system including a portion that contains several X-ray sources and line detectors for detecting the opacity to radiation in a series of planes intersecting an object under test. The signals detected are processed to produce an opacity map of the object.